5 Author: Pekka Riikonen <priikone@silcnet.org>
7 Copyright (C) 1997 - 2001 Pekka Riikonen
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; version 2 of the License.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
20 /****h* silccore/SilcPacketAPI
24 * Implementation of the packet routines for sending and receiving
25 * SILC Packets. These includes the data sending routines and data
26 * reading routines, encrypting and decrypting routines, packet assembling
27 * and packet parsing routines.
34 /* Default byte size of the packet. */
35 #define SILC_PACKET_DEFAULT_SIZE SILC_SOCKET_BUF_SIZE
37 /* Header length without source and destination ID's. */
38 #define SILC_PACKET_HEADER_LEN 8 + 2
40 /* Minimum length of SILC Packet Header. This much is decrypted always
41 when packet is received to be able to get all the relevant data out
43 #define SILC_PACKET_MIN_HEADER_LEN 16 + 2
45 /* Maximum padding length */
46 #define SILC_PACKET_MAX_PADLEN 16
48 /* Minimum packet length */
49 #define SILC_PACKET_MIN_LEN (SILC_PACKET_HEADER_LEN + 1)
51 /* Maximum length of ID */
52 #define SILC_PACKET_MAX_ID_LEN 16
54 /****d* silccore/SilcPacketAPI/SilcPacketType
58 * typedef unsigned char SilcPacketType;
62 * SILC packet type definition and all the packet types.
66 typedef unsigned char SilcPacketType;
68 /* SILC Packet types. */
69 #define SILC_PACKET_NONE 0 /* NULL, never sent */
70 #define SILC_PACKET_DISCONNECT 1 /* Disconnection */
71 #define SILC_PACKET_SUCCESS 2 /* Success */
72 #define SILC_PACKET_FAILURE 3 /* Failure */
73 #define SILC_PACKET_REJECT 4 /* Rejected */
74 #define SILC_PACKET_NOTIFY 5 /* Notify message */
75 #define SILC_PACKET_ERROR 6 /* Error message */
76 #define SILC_PACKET_CHANNEL_MESSAGE 7 /* Message for channel */
77 #define SILC_PACKET_CHANNEL_KEY 8 /* Key of the channel */
78 #define SILC_PACKET_PRIVATE_MESSAGE 9 /* Private message */
79 #define SILC_PACKET_PRIVATE_MESSAGE_KEY 10 /* Private message key*/
80 #define SILC_PACKET_COMMAND 11 /* Command */
81 #define SILC_PACKET_COMMAND_REPLY 12 /* Reply to a command */
82 #define SILC_PACKET_KEY_EXCHANGE 13 /* Start of KE */
83 #define SILC_PACKET_KEY_EXCHANGE_1 14 /* KE1 */
84 #define SILC_PACKET_KEY_EXCHANGE_2 15 /* KE2 */
85 #define SILC_PACKET_CONNECTION_AUTH_REQUEST 16 /* Request of auth meth */
86 #define SILC_PACKET_CONNECTION_AUTH 17 /* Connectinon auth */
87 #define SILC_PACKET_NEW_ID 18 /* Sending new ID */
88 #define SILC_PACKET_NEW_CLIENT 19 /* Client registering */
89 #define SILC_PACKET_NEW_SERVER 20 /* Server registering */
90 #define SILC_PACKET_NEW_CHANNEL 21 /* Channel registering */
91 #define SILC_PACKET_REKEY 22 /* Re-key start */
92 #define SILC_PACKET_REKEY_DONE 23 /* Re-key done */
93 #define SILC_PACKET_HEARTBEAT 24 /* Heartbeat */
94 #define SILC_PACKET_KEY_AGREEMENT 25 /* Key Agreement request */
95 #define SILC_PACKET_RESUME_ROUTER 26 /* Backup router resume */
96 #define SILC_PACKET_FTP 27 /* File Transfer */
98 #define SILC_PACKET_PRIVATE 200 /* Private range start */
99 #define SILC_PACKET_MAX 255 /* RESERVED */
102 /****d* silccore/SilcPacketAPI/SilcPacketVersion
106 * typedef unsigned char SilcPacketVersion;
110 * SILC packet version type definition.
113 typedef unsigned char SilcPacketVersion;
115 /****d* silccore/SilcPacketAPI/SilcPacketFlags
119 * typedef unsigned char SilcPacketFlags;
123 * SILC packet flags type definition and all the packet flags.
127 typedef unsigned char SilcPacketFlags;
129 /* All defined packet flags */
130 #define SILC_PACKET_FLAG_NONE 0x00 /* No flags */
131 #define SILC_PACKET_FLAG_PRIVMSG_KEY 0x01 /* Private message key */
132 #define SILC_PACKET_FLAG_LIST 0x02 /* Packet is a list */
133 #define SILC_PACKET_FLAG_BROADCAST 0x04 /* Packet is a broadcast */
136 /* Rest of flags still available
137 #define SILC_PACKET_FLAG_XXX 0x08
138 #define SILC_PACKET_FLAG_XXX 0x10
139 #define SILC_PACKET_FLAG_XXX 0x20
140 #define SILC_PACKET_FLAG_XXX 0x40
141 #define SILC_PACKET_FLAG_XXX 0x80
144 /****s* silccore/SilcPacketAPI/SilcPacketContext
148 * typedef struct { ... } SilcPacketContext;
152 * In packet sending this is filled and sent to silc_packet_assemble
153 * which then uses it to assemble new packet. In packet reception pointer
154 * to this context is sent to silc_packet_parse which parses the packet
155 * and returns the relevant information to this structure. On packet
156 * reception returned ID's are always the hash values of the ID's from
159 * Short description of the fields following:
165 * SilcPacketType type
167 * Type of the packet. Types are defined below.
169 * SilcPacketFlags flags
171 * Packet flags. Flags are defined above.
173 * unsigned char *src_id
175 * unsigned char src_id_type
177 * Source ID, its length and type. On packet reception retuned ID's
178 * are always the hash values of the ID's from the packet.
180 * unsigned char *dst_id;
182 * unsigned char src_id_type;
184 * Destination ID, its length and type. On packet reception retuned
185 * ID's are always the hash values of the ID's from the packet.
190 * The true lenght of the packet and the padded length of the packet.
191 * These may be set by the caller before calling any of the
192 * silc_packet_* routines. If not provided the library will calculate
197 * Reference counter for this context. The context is freed only
198 * after the reference counter hits zero. The counter is added
199 * calling silc_packet_context_dup and decreased by calling the
200 * silc_packet_context_free.
204 * Packet sequence number.
210 SilcPacketFlags flags;
212 unsigned char *src_id;
214 unsigned char src_id_type;
216 unsigned char *dst_id;
218 unsigned char dst_id_type;
225 SilcSocketConnection sock;
232 /****s* silccore/SilcPacketAPI/SilcPacketParserContext
236 * typedef struct { ... } SilcPacketParserContext;
240 * This context is used in packet reception when silc_packet_receive_process
241 * function calls parser callback that performs the actual packet decryption
242 * and parsing. This context is sent as argument to the parser function.
243 * This context must be free'd by the parser callback function.
245 * Following description of the fields:
247 * SilcPacketContext *packet
249 * The actual packet received from the network. In this phase the
250 * context is not parsed, only the packet->buffer is allocated and
251 * it includes the raw packet data, which is encrypted.
253 * SilcSocketConnection sock
255 * The associated connection.
259 * User context that is sent to the silc_packet_receive_process
260 * function. This usually includes application and connection specific
265 SilcPacketContext *packet;
266 SilcSocketConnection sock;
268 } SilcPacketParserContext;
270 /****f* silccore/SilcPacketAPI/SilcPacketParserCallback
274 * typedef void (*SilcPacketParserCallback)(SilcPacketParserContext
279 * This callback is given to the silc_packet_receive_process function.
280 * The callback is called by the library every time a packet is
281 * received from the network. After the packet has been decrypted
282 * and at least partially parsed it is passed to the application
283 * for further parsing using this callback and the SilcPacketParserContext
284 * context. The application receiving the SilcPacketParserContext
288 typedef void (*SilcPacketParserCallback)(SilcPacketParserContext
291 /****f* silccore/SilcPacketAPI/SilcPacketCheckDecrypt
295 * typedef int (*SilcPacketCheckDecrypt)(SilcPacketType packet_type,
297 * SilcPacketContext *packet,
302 * This callback function relates to the checking whether the packet is
303 * normal packet or special packet and how it should be processed. If
304 * the callback returns TRUE the packet is normal and FALSE if the packet
305 * is special and requires special procesing. Some of the packets in
306 * SILC are special (like channel message packets that are encrypted
307 * using channel specific keys) and requires special processing. That
308 * is the reason for this callback function.
310 * The library will call this function if provided for the
311 * silc_packet_decrypt function. The `packet_type' is the type of
312 * packet received (this is also actually the first time application
313 * receives information of the received packet, next time it receives
314 * it is when the SilcPacketParserCallback function is called),
315 * the `buffer' is the raw packet data the `packet' the allocated
316 * SilcPacketContext that is filled when parsing the packet and `context'
317 * is application specific user context.
320 typedef int (*SilcPacketCheckDecrypt)(SilcPacketType packet_type,
322 SilcPacketContext *packet,
327 /****d* silccore/SilcPacketAPI/SILC_PACKET_LENGTH
331 * #define SILC_PACKET_LENGTH ...
335 * Returns true length of the packet and padded length of the packet.
336 * This is primarily used by the libary in packet parsing phase but
337 * the application may use it as well if needed.
341 #define SILC_PACKET_LENGTH(__packet, __ret_truelen, __ret_padlen) \
343 SILC_GET16_MSB((__ret_truelen), (__packet)->data); \
344 (__ret_padlen) = (((__ret_truelen) - 2) + \
345 SILC_PACKET_MAX_PADLEN) & ~(SILC_PACKET_MAX_PADLEN - 1); \
349 /****d* silccore/SilcPacketAPI/SILC_PACKET_PADLEN
353 * #define SILC_PACKET_PADLEN ...
357 * Returns the length of the padding in the packet. This is used
358 * by various library routines to determine needed padding length.
362 #define SILC_PACKET_PADLEN(__packetlen) \
363 SILC_PACKET_MAX_PADLEN - ((__packetlen) - 2) % SILC_PACKET_MAX_PADLEN;
368 /****f* silccore/SilcPacketAPI/silc_packet_send
372 * int silc_packet_send(SilcSocketConnection sock, bool force_send);
376 * Actually sends the packet. This flushes the connections outgoing data
377 * buffer. If data is sent directly to the network this returns the bytes
378 * written, if error occured this returns -1 and if the data could not
379 * be written directly to the network at this time this returns -2, in
380 * which case the data should be queued by the caller and sent at some
381 * later time. If `force_send' is TRUE this attempts to write the data
382 * directly to the network, if FALSE, this returns -2.
385 int silc_packet_send(SilcSocketConnection sock, bool force_send);
387 /****f* silccore/SilcPacketAPI/silc_packet_encrypt
391 * void silc_packet_encrypt(SilcCipher cipher, SilcHmac hmac,
392 * SilcBuffer buffer, uint32 len);
396 * Encrypts a packet. This also creates HMAC of the packet before
397 * encryption and adds the HMAC at the end of the buffer. This assumes
398 * that there is enough free space at the end of the buffer to add the
399 * computed HMAC. This is the normal way of encrypting packets, if some
400 * other process of HMAC computing and encryption is needed this function
404 void silc_packet_encrypt(SilcCipher cipher, SilcHmac hmac,
405 SilcBuffer buffer, uint32 len);
407 /****f* silccore/SilcPacketAPI/silc_packet_assemble
411 * void silc_packet_assemble(SilcPacketContext *ctx);
415 * Assembles a new packet to be ready for send out. The buffer sent as
416 * argument must include the data to be sent and it must not be encrypted.
417 * The packet also must have enough free space so that the SILC header
418 * and padding maybe added to the packet. The packet is encrypted after
419 * this function has returned.
421 * The buffer sent as argument should be something like following:
423 * --------------------------------------------
424 * | head | data | tail |
425 * --------------------------------------------
429 * So that the SILC header and 1 - 16 bytes of padding can fit to
430 * the buffer. After assembly the buffer might look like this:
432 * --------------------------------------------
434 * --------------------------------------------
436 * Start of assembled packet
438 * Packet construct is as follows (* = won't be encrypted):
440 * n bytes SILC Header
441 * 2 bytes Payload length (*)
444 * 2 bytes Source ID Length
445 * 2 bytes Destination ID Length
446 * 1 byte Source ID Type
448 * 1 byte Destination ID Type
449 * n bytes Destination ID
451 * 1 - 16 bytes Padding
453 * n bytes Data payload
455 * All fields in the packet will be authenticated by MAC. The MAC is
456 * not computed here, it must be computed separately before encrypting
460 void silc_packet_assemble(SilcPacketContext *ctx);
462 /****f* silccore/SilcPacketAPI/silc_packet_send_prepare
466 * void silc_packet_send_prepare(SilcSocketConnection sock,
473 * Prepare outgoing data buffer for packet sending. This moves the data
474 * area so that new packet may be added into it. If needed this allocates
475 * more space to the buffer. This handles directly the connection's
476 * outgoing buffer in SilcSocketConnection object.
479 void silc_packet_send_prepare(SilcSocketConnection sock,
484 /****f* silccore/SilcPacketAPI/silc_packet_receive
488 * int silc_packet_receive(SilcSocketConnection sock);
492 * Receives packet from network and reads the data into connection's
493 * incoming data buffer. If the data was read directly this returns the
494 * read bytes, if error occured this returns -1, if the data could not
495 * be read directly at this time this returns -2 in which case the data
496 * should be read again at some later time, or If EOF occured this returns
500 int silc_packet_receive(SilcSocketConnection sock);
502 /****f* silccore/SilcPacketAPI/silc_packet_decrypt
506 * int silc_packet_decrypt(SilcCipher cipher, SilcHmac hmac,
507 * SilcBuffer buffer, SilcPacketContext *packet,
508 * SilcPacketCheckDecrypt check_packet,
513 * Decrypts a packet. This assumes that typical SILC packet is the
514 * packet to be decrypted and thus checks for normal and special SILC
515 * packets and can handle both of them. This also computes and checks
516 * the HMAC of the packet. If any other special or customized decryption
517 * processing is required this function cannot be used. This returns
518 * -1 on error, 0 when packet is normal packet and 1 when the packet
519 * is special and requires special processing.
521 * The `check_packet' is a callback funtion that this function will
522 * call. The callback relates to the checking whether the packet is
523 * normal packet or special packet and how it should be processed. If
524 * the callback return TRUE the packet is normal and FALSE if the packet
525 * is special and requires special procesing.
528 int silc_packet_decrypt(SilcCipher cipher, SilcHmac hmac,
529 SilcBuffer buffer, SilcPacketContext *packet,
530 SilcPacketCheckDecrypt check_packet,
533 /****f* silccore/SilcPacketAPI/silc_packet_receive_process
537 * void silc_packet_receive_process(SilcSocketConnection sock,
538 * SilcCipher cipher, SilcHmac hmac,
539 * SilcPacketParserCallback parser,
544 * Processes the received data. This checks the received data and
545 * calls parser callback that handles the actual packet decryption
546 * and parsing. If more than one packet was received this calls the
547 * parser multiple times. The parser callback will get context
548 * SilcPacketParserContext that includes the packet and the `context'
549 * sent to this function.
552 void silc_packet_receive_process(SilcSocketConnection sock,
553 SilcCipher cipher, SilcHmac hmac,
554 SilcPacketParserCallback parser,
557 /****f* silccore/SilcPacketAPI/silc_packet_parse
561 * SilcPacketType silc_packet_parse(SilcPacketContext *ctx);
565 * Parses the packet. This is called when a whole packet is ready to be
566 * parsed. The buffer sent must be already decrypted before calling this
567 * function. The len argument must be the true length of the packet. This
568 * function returns the type of the packet. The data section of the
569 * buffer is parsed, not head or tail sections.
572 SilcPacketType silc_packet_parse(SilcPacketContext *ctx);
574 /****f* silccore/SilcPacketAPI/silc_packet_parse_special
578 * SilcPacketType silc_packet_parse_special(SilcPacketContext *ctx);
582 * Perform special SILC Packet header parsing. This is required to some
583 * packet types that have the data payload encrypted with different key
584 * than the header area plus padding of the packet. Hence, this parses
585 * the header in a way that it does not take the data area into account
586 * and parses the header and padding area only.
589 SilcPacketType silc_packet_parse_special(SilcPacketContext *ctx);
591 /****f* silccore/SilcPacketAPI/silc_packet_context_alloc
595 * SilcPacketContext *silc_packet_context_alloc();
599 * Allocates a packet context. Packet contexts are used when
600 * packets are assembled and parsed. The context is freed by the
601 * silc_packet_context_free function.
604 SilcPacketContext *silc_packet_context_alloc(void);
606 /****f* silccore/SilcPacketAPI/silc_packet_context_dup
610 * SilcPacketContext *silc_packet_context_dup(SilcPacketContext *ctx);
614 * Duplicates the packet context. It actually does not duplicate
615 * any data, instead a reference counter is increased.
618 SilcPacketContext *silc_packet_context_dup(SilcPacketContext *ctx);
620 /****f* silccore/SilcPacketAPI/silc_packet_context_free
624 * void silc_packet_context_free(SilcPacketContext *ctx);
628 * Frees the packet context. The context is actually freed when the
629 * reference counter hits zero.
632 void silc_packet_context_free(SilcPacketContext *ctx);